Once it might have been thought that a musical tale about an aspiring 11-year-old dancer set during the miners' strike would have limited, perhaps niche, appeal. Then Billy Elliot sprang on to the silver screen. Next he took to the stage. Now, five years on from the story's West End debut, it is a global phenomenon.

Tomorrow night 19 Billy Elliots – past, present and future – will appear together in London to celebrate the birthday of the live production. After that, fans in South Korea, Japan, Germany and Holland await Billy's arrival.

The three men responsible, Stephen Daldry as director, Lee Hall as writer and Elton John as composer, are to join current and former cast members and their families for what promises to be an emotional and chaotic night at the Victoria Palace theatre.

"We're doing it to get back as many as we can of the kids who performed in London," Daldry said. "I suppose you'd call the finale we're planning a Billy megamix.

"It will be very moving. A lot of these boys are big boys now, the oldest is 20, he's in Dirty Dancing. It was such a unique moment in their lives and of course it's astonishing to see them all grown up. When we have these get-togethers it's like a big Polish wedding. It's huge fun."

The musical, based on the successful film, opened five years ago and since then 22 boys have played the part of Billy on the London stage. A Sydney version of the show followed in 2007 and the hugely successful Broadway version – it won 10 Tonys – in 2008. Next up is Chicago, from where Daldry has just returned for tomorrow's very special show.

He said the timing was good. It is a production that resonates ever more loudly with the times. The first number has banners saying Save Our Community and Americans get that, particularly in Chicago, said Daldry. "That blue-collar audience really understands it, that their industries and communities are under threat."

But Daldry admits surprise at just how much American audiences love the show. "It is basically a strong piece of political theatre which is not even-handed and is not pretending to be even-handed. It wears its heart and politics on its sleeve."

It is also, of course, an almost absurdly moving story of one boy achieving his dream of becoming a ballet dancer in the face of adversity – one that has encouraged producers to venture into foreign-language productions with Korea in August, Japan in 2011, to be followed by Germany and Holland.

It is not an easy process. Daldry said: "The issue with the show is that it is hand-made each time and it has to be hand-made because of the children. It's not a show that can be mass-manufactured. In some senses we all wish it was because we wouldn't have to worry about it so much. The emotional investment everybody makes is huge, it has to be huge. It's not Mamma Mia! It is not a contained production that is easy to maintain. This is a nightmare to maintain. And it's expensive."

To give an example, Daldry reels off the problems encountered in Chicago. "There are 160 of us in Chicago, in that we've had to move there to put the show on. I know, it's insane. But if you just look at it from the kids' point of view you have ballet teachers, tap teachers, gymnastic teachers, choreographers, then there's the academic teachers, their chaperones, their parents, the physiotherapists. It just goes on and on and on."

Part of its Broadway success, Daldry believes, is that they have remained faithful to the original and all the actors have to master an accent that is difficult to get right – Geordie. "We take a lot of care over it. The actors have dialect training even before they come in to the audition. What the American audience wants is authenticity. The idea that they would want a pale imitation of an English show is nonsense."

Part of the challenge for future productions will be finding the dialect equivalent of Geordie in countries like Japan.

Daldry is one of Britain's most respected film and theatre directors and has been nominated for an Oscar for each of his three movies – Billy Elliot, The Hours and The Reader. Like many others, he sees a West End that is in good shape with strong productions and record audience numbers. "There is a strength within the leadership of our subsidised sectors that is really feeding the West End. Whether that's the Young Vic or the National Theatre or the Donmar or the Royal Court. It's about the leadership of those organisations as much as the funding of those organisations."

But we should enjoy it while it lasts. "There are draconian cuts round the corner which everyone is bracing themselves for. The boom that we are currently seeing could well turn into a retreat because the government will cut. It is totally inevitable. It will cut schools, it will cut healthcare, it will cut the armed forces, so it will have to cut the arts."

Politicians have not been shy in trying to grab some of the Billy action. Earlier this month four Billys were invited to Downing Street to meet Gordon Brown, Alistair Darling and Peter Mandelson. John Prescott was a regular showgoer and even Tories have been in the audience. "Boris Johnson thought it was a total misrepresentation," said Daldry. "We were very happy about that."

But it was not until recently that someone central to the show, Arthur Scargill, came to see it. "He loved it and I was really pleased by that."

Daldry is immersed in Billy Elliot but has other irons in the fire, including talking to Disney about a musical version of Dumbo. "I want to do Dumbo. Dumbo's fantastic because it's weird and dark and deeply moving. It's one of the oddest Disney movies, I think."

Before then will be another film but he is reluctant to say what it might be. "You never know you're doing a movie until you're actually physically doing it. There are so many reasons for it not to be made."

Daldry returns to Chicago at the weekend to continue putting the cast through its paces. The Billys over there are Swiss, Mexican, Canadian and Chinese. "We get plaudits for diversity of casting but it's just something we have to do, we have to cast the best kids."

It has become a huge part of Daldry's life. "The funny thing about Billy Elliot I can honestly say, in these five years, I've had the best nights of my life in the theatre. Particularly when a new child gets into the show and you watch them doing well. It is blissful."